This invention relates to the printing industry, and in particular, to a new lightweight portable and compact flexographic printer coater for movement to any printing unit on a multi-unit rotary offset lithographic printing press for inking or coating purposes.
Offset lithography is a process well known in the art which utilizes the planographic method. Image and non-printing areas are essentially on the same plane of a thin metal plate and the distinction between them is maintained chemically. Ink is offset from a plate on the plate cylinder to a rubber blanket on a blanket cylinder and then from the blanket to a substrate supported on an impression cylinder on which printing occurs.
Conventional sheet-fed, rotary offset printing presses typically include one or more printing units through which individual sheets are fed and printed. After the last printing unit, freshly printed sheets are transferred by a delivery conveyor to the delivery end of the press where they are collected and stacked uniformly. In a typical sheet-fed, rotary offset printing press, the delivery conveyor includes endless chains carrying gripper bars with gripper fingers which grip and pull freshly printed sheets from the last impression cylinder and convey them to the sheet delivery stacker.
Printed lithographic ink on the surface of the substrate sheet dries relatively slowly through oxidation and is easily smeared by subsequent transfer cylinders between the individual printing units of the press. Any relative movement of the freshly printed surface relative to a support surface can result in smearing. Modified and specialized equipment and techniques have been developed to combat this problem.
A related problem that is faced in the prior art is the problem of xe2x80x9coffsettingxe2x80x9d and xe2x80x9cset offxe2x80x9d of freshly printed ink at the delivery end of the press after the printed sheets are collected and stacked. A similar problem occurs in roll form material produced on a web-fed press. In some printing jobs, offsetting is prevented by applying a protective and/or decorative coating material over all or a portion of the freshly printed sheets. Some coatings are formed of an ultra-violet (UV)-curable or water-dispersed resin applied as a liquid solution over the freshly printed sheets to protect the ink from offsetting or set-off and improve the appearance of the freshly printed sheets. Such coatings are particularly desirable when decorative or protective finishes are applied in the printing of posters, record jackets, brochures, magazines, folding cartons and the like. In cases where coating is to be applied, the coating operation is carried out after the last printing unit, most desirably by an in-line coating application. It is highly undesirable to process the sheet through the press a second time in order to apply coatings, although this is sometimes done for special effects that are not otherwise obtainable.
The ability to overall coat, spot coat or print with aqueous, flexographic and UV curable inks and/or coatings in combination with lithographic, flexographic and waterless printing processes on a rotary offset printing press is highly desirable. Flexographic printing or coating with aqueous, flexographic and UV curable inks from a blanket or a relief plate can permit much heavier wet and dried ink film layers on the substrate. This is largely due to the nature of lithographic inks. Lithographic inks are generally oil based inks that are formulated to print from planographic surfaces based on the principle that oil and water do not mix. Lithographic inks are generally very strong in color value to compensate for the lesser amount that is printed. They are among the strongest of all inks. The average amount of ink transferred to the paper is further diluted by the double split of the ink film between the plate cylinder and the blanket cylinder and between the blanket cylinder and the substrate to be printed in the nip between the blanket cylinder and the impression cylinder. In many situations, only a quarter of the film thickness on the plate is transferred to the substrate. This can make it difficult to obtain sufficient opacity with white or metallic (gold, silver or other metallic) ink or in printing specialized vehicles such as xe2x80x9cscratch-and-sniffxe2x80x9d materials from a slurry containing encapsulated essence. This often means that sheets or substrate must be removed and transferred to a second type of machine using the flexographic process to apply greater amounts of ink thickness or the sheets must make successive or two or more passes on a lithographic press to achieve desired print quality.
The prior art has attempted to solve these problems to obtain higher applied film weights on lithographic printing presses in a variety of ways.
For example, it is known to provide a printing machine with a downstream coating station having a blanket roller coater associated with a coating application unit for application of a protective coating over the entire printed area of copy sheets or web before they go to the stacker. Jahn, U.S. Pat. Nos. 4,615,293 and 4,706,601 disclose separate duplex coating units disposed downstream of a printing press. These permit coating selected portions of the substrate using a relief plate and they permit blanket coating.
A number of coating units are known which are appended to or mounted upon the final printing station in the press. Most of these coating units prevent the printing unit on which it is mounted from doing its normal printing function resulting in the loss of one printed color. A four color press using such a coating apparatus would permit printing only three colors in line in a single pass operation because the last station is converted to a flexographic printer-coater. Bird, U.S. Pat. Nos. 4,796,556 and 4,841,903 disclose a liquid application station for the final downstream printing station which converts the lithographic station to a printing coater or a continuous film coater by moving a carriage having a coating unit into impression with the plate or blanket cylinder of the last station on the press. When the coater is used, the normal lithographic printing function on that station is inoperative. DiRico, U.S. Pat. No. 4,685,414 discloses a process and apparatus in use in combination with the last station of an existing offset lithographic press where the coating means is retractable to be used or not as a printer requires. Since the DiRico coater utilizes a blanket cylinder on the last unit of the press, this last unit cannot be used for color printing when it is used for coating. DeMoore, et al., U.S. Pat. No. 5,651,316 discloses a retractable printer-coater unit which though not limited to the last printing station of an offset lithographic press, is useful for lithographic or flexographic printing when the ordinary lithographic operation of the station in which it is mounted is not being used. The lithographic operation of the station is lost when this printer-coater is in operation. Sarda, U.S. Pat. No. 4,889,051 illustrates a retractable lithographic printing unit which does not disable normal lithographic printing on the lithographic printing station. It enables printing another lithographic color at a station by adding a second blanket roller and a retracting inked and dampened applicator for the second blanket roller of the printing station.
Koehler, et al., U.S. Pat. Nos. 4,934,305 and 5,178,678 disclose a flexographic liquid film applicator unit which employs a special xe2x80x9cblanketxe2x80x9d cylinder which engages the substrate on the impression cylinder of the last lithographic printing station on a multicolor lithographic press. The unit slides in and out on xe2x80x9cinclined tracksxe2x80x9d. Manual reengagement and registration of a drive gear on the applicator with a press drive gear using xe2x80x9cindexxe2x80x9d marks is required to reset the applicator xe2x80x9cblanketxe2x80x9d cylinder after the unit has been moved away from the printing station.
DeMoore, et al., U.S. Pat. No. 5,176,077 is a delivery cylinder coater for use on the final printing station of a lithographic printing press. The delivery cylinder is provided with a coating blanket. A flexographic applicator roll applies liquid coating to the delivery cylinder as it rotates into the freshly lithographically inked surface of the sheets coming off the press. The coating pickup anilox roller frictionally engages the surface of the delivery cylinder and is rotated by a hydraulic motor.
Much of the prior art has disadvantages. Retrofitting existing presses is often difficult because of space considerations, especially between printing units. A dedicated coating unit is often not possible because of limited space and involves press downtime and substantial capital costs. Retrofitted devices that utilize the print cylinder or blanket cylinder of the press can limit the ability of that station to lithographically print in the normal manner.
Coaters which utilize the plate cylinder or the blanket cylinder of the printing unit still suffer from the disadvantage that the coating is split which reduces the wet film thickness that can be applied to the substrate itself. A few add on coating units that print directly on the substrate on the impression cylinder or a transfer cylinder are limited to the last printing station on the press where there is more room for installation. Such equipment can be moved away or the operator can do the make ready work on the opposite side of the last printing station in the conventional work space for the operator. If such equipment is mounted in the interstation space on a lithographic press, the equipment interferes with operator access to the next station.
Much of the prior art consumes large areas of space on the press, both between printing units and in some instances in the overhead area. Because of the complexity and size of equipment, limited locations are available for which it can be used. Additionally, the prior art devices are heavy; thus, when installing these devices, cranes or similar equipment are often required to properly mount the devices in position. A further disadvantage is that these devices are expensive to manufacture and maintain. Finally, the prior art devices are not designed as portable devices for placement on different printing presses or on different printing units. Most printer coater devices are attached to a single printing unit and require extensive connections that must be disconnected requiring extensive labor and costs. Also, as stated previously, each time a printer coater is moved, a crane or other transport device is required to remove and carry the printer coater to a different printing unit.
It is preferable not to have to cut into press frame to gain access to the main gears and not to have to manually engage and disengage indexed gear teeth of gears on the coater with gears on the press. The ability to flexographically coat, spot coat or print on the substrate at an intermediate printing station with an apparatus that is inexpensive and compact so that it can fit into small areas is highly desirable. It is also desirable to have a lightweight and portable device so that it can be carried by humans for use on any printing unit of a lithographic printing press or to a completely different printing press of the same size and installed or removed without the use of heavy equipment. The present invention is able to fulfill these needs and more.
The present invention provides a portable universal apparatus for application of flexographic inking or coating substances to printed material on a lithographic printing press, such as those manufactured by Heidelberg Speedmaster, Komori, M.A.N. Rowland, Mitsubishi and other presses of the same nominal width. The apparatus is configured to be placed on any printing unit of a rotary offset lithographic printing press with minimal modification to the printing press. The apparatus is compact, inexpensive and lightweight to allow portability so that it may be transported and used on any printing unit of the printing press or transported to a different printing press which is manufactured by the same or a different manufacturer. The printer coater itself is designed for a given printing format.
The entire printer coater apparatus is constructed as a unit and includes a liquid chamber to hold printing liquid, an applicator roller to receive and apply the printing liquid to a rotating printing surface, a means to drive or rotate the applicator roller and a positioner device to place the printer coater between the on and off-impression positions. The printer coater apparatus comprises a movable frame to support and hold the components of the apparatus. A rotating printing surface is meant to include a plate on the plate cylinder or a plate or blanket on the blanket cylinder as the printer coater apparatus may be installed adjacent a plate cylinder or adjacent a blanket cylinder.
The applicator roller is most preferably a lightweight anilox roller made of a non-metallic composite material. The roller surface is designed to be wear resistant and capable of applying the printing ink or coating material to the rotating printing surface. The anilox roller is journaled into the printer coater side members so that it is capable of rotation by a remotely controlled electrical motor, also mounted onto the frame of the printer coater apparatus. Rotation of the anilox roller is most preferably performed by an electrical motor, however, an equivalent means such as a hydraulic motor may be used.
The liquid chamber, also mounted to the printer coater frame, provides a means to apply the inking or coating to the anilox roller. Attached to the liquid chamber by a quick connect mechanism are a pair of flexible conduits for supplying inking or coating liquid to the chamber. One hose supplies liquid to the inking chamber that is pumped from a remote reservoir and the other hose is connected to a vacuum pump and used to re-circulate unused fluid back to the remote reservoir for maintaining a fresh supply of inking or coating substance.
A positioner device carried by the printer coater frame moves the printer coater apparatus between the on and off-impression positions. When in the on-impression position, the coating or inking substance is applied to a rotating printing surface. When placed in the off-impression position, the printer coater is retracted from the rotating printing surface to stop liquid application. The positioner device most preferably comprises a pneumatically operated cylinder; however, other devices such as a hydraulically or electrically operated device may be used. In order to establish the on-impression position for the printer coater, an adjustable on-stop is mounted on each side of the printer coater frame which cooperates with a stop surface on the fixed support.
The printer coater attaches to the printing press with little modification to the press frame. Fixed supports are mounted on the interior surface of the press frame adjacent a rotating printing surface, one on the drive side and the other on the operator side of the press frame. Each fixed support member comprises a rail so that the printer coater may slide upon as it is inserted and moved into the printing unit. The fixed supports serve two main purposes: to provide a xe2x80x9ctrackxe2x80x9d for sliding the printer coater into the right position and to support the printer coater while mounted in the printer unit. A pair of fixed supports can be mounted unobtrusively on each and every printing unit so the printer coater can be removed from one unit and immediately installed on a different printing unit. These fixed supports do not interfere with access to the printing unit when the printer coater is removed from the printing unit.
Connected to the bottom of the printer coater apparatus is a pair of lock-on members that releasably connect the printer coater frame with the fixed supports. The lock-on members serve as an anchor for relative movement of the printer coater apparatus as it is moved by the positioner on and off-impression.
Mounted on the printer coater frame end members are handles that allow the users to carry the printer coater apparatus. The unit weights approximately 85 pounds and can be easily carried and transported by two humans. Most preferably, the printer coater apparatus is mounted adjacent the blanket cylinder delivery side for best performance and results. However, other appropriate locations for mounting the apparatus include the feed side of the blanket cylinder and adjacent the plate cylinder.
Often different press manufacturers for printing presses of the same nominal printing width will have varying lengths between the interior sides of a press frame. The present invention can be adapted for use on any printing press of the same nominal printing width, regardless of the press manufacturer. Thus, it is unnecessary to construct additional printer coaters. In order to compensate for larger press widths, spacers of various thickness can be mounted between the fixed supports and the interior surfaces of the press frame. In addition, the fixed supports can be made of varying thickness so that spacers are not necessary.